“Kids speak when chickens pee.”

This expression implies that someone should be quiet, as it suggests something that never happens (chickens don't pee), thus they should remain silent.

Translation in spanish

“Los niños hablan cuando las gallinas meen.”

Esta expresión implica que alguien debe quedarse callado, ya que sugiere algo que nunca sucede (las gallinas no mean), por lo tanto, deben permanecer en silencio.

Phonetic:
/Lohs nee-nyos ah-blahn kwahn-doh lahs gah-yee-nahs meh-en/